The present invention relates to a new and improved chromium containing alloy for use as a pressing tool, especially a pressure plate, chemically or electrochemically treated pressing tools formed therefrom, and a method of fabricating such pressing tools.
Pressing tools and especially pressing plates comprise either a working surface which is burnished or polished to high luster in the event that the pressed object or article like, for example, a furniture plate is intended to inherently have a smooth surface or such pressing tools are structured so that the pressed article then has a comparable structured surface. It is required for the manufacture of such structured pressing tools, such as pressing tools including a polished planar surface, to first produce a surface which is as smooth as possible and only contains a slight roughness. Subsequently, the pressing tool is processed according to known methods like, for example, electrochemical or purely chemical methods. During such processing it is of particular significance that the material is removed in the desired amount. Even if there are only insignificant differences between the actual and the desired material removal, there will occur considerable flaws in the optical impression because in many cases the pressed material is intended to communicate the impression or appearance of a certain structure, for example, the graining of wood, be it in a processed state or in the original state, or a granular structure like that of sandstone or the like. When such article impression or appearance is flawed by non-uniform material removal from the pressing tool, then, the pressing tool generally can not be again reprocessed to possess the desired surface properties, wherefore such pressing tool must be rejected for further use.
As a material for the pressing plates burnished or high-luster polished chromium steels containing chromium in an amount of 11 to 17.5% have proven useful. When such chromium steels, however, are surface treated according to one of the conventional methods, for example, by etching, such pressure plates contain substantial structural imperfections.